174 CALIFORNIA ACADEMY OF SCIENCES [Proc. 30 Ser. 



Etchegoin Beds j San Joaquin Clays 



(San Pablo Beds ?) I Etchegoin Sands 



Coalinga Beds \ Oyster Sands, etc. 



( Reef Beds, etc. 



Each of these divisions could be again subdivided with 

 greater or less success w^ithin specified limits, but it would be 

 difficult to discover features characteristic enough for such 

 purposes that would have a wide application. In other words, 

 the materials of the strata change more or less from point to 

 point along their strike, passing from coarser to finer, etc., 

 according to local conditions during the period of their depo- 

 sition, such as the presence of streams, currents, etc. 



The most constant feature of the lower two-thirds of the 

 combined series is its sandy character, while the upper por- 

 tion is clay or fine sand and clay, in which the clays are 

 variegated in color, being alternately white, red, gray, or 

 yellow. 



Co a Ibiga Beds . 



An interesting stratigraphic unit is that here described 

 as the Coalinga Beds. So far they have been found only 

 locally, and throughout a stretch of more than fifty miles 

 along the Mount Diablo Range they were not recognized 

 at all. They occur, however, in both the Coalinga and 

 McKittrick districts, and in each case sufficiently individual- 

 ized to be regarded as distinct from both the Monterey and 

 the Etchegoin Beds. 



In the Coalinga district, as shown on the map (PL xxxv), 

 the formation occurs in two separate areas, the more north- 

 ern of which can be followed far beyond the limits of the 

 map, or at least to the Cantua Creek if not to Mount Diablo. 



West of Coalinga these beds are sandy with a minor part 

 of shale, which at one place north of the coal mine appears 

 to be soft and marly if not diatomaceous. At the artesian 

 water well on Section 35 these marly beds do not appear, 

 but the basal beds are composed of sands which are locally 

 bituminous. Six miles north, on the E. J^ of Sec. 36 marly 

 beds crop out very near the base and present also a strongly 



